The Study Of Combustion Instability In The Tiny Oil Combustion Chamber

Flame combustion instability phenomenon is common exit in various burner, cause of burner structure fatigue damage and combustion efficiency drops. This phenomenon is also exit in the tiny oil ignition burner practical application, so the study flame combustion was carry out in the view of structure and flame unsteady combustion.The study of unsteady combustion are based on the method of theoretical analysis and numerical simulation, thermal acoustic oscillations theoretical model are established, burner for modal analysis are carry out by mechanical analysis software-Mechanical for the structure natural frequency and formations, flame combustion instability phenomena are acquired by CFD numerical simulation.First of all, combustion instability theory analysis, wave equation that can describe the sound of the phenomenon of oil combustion chamber coupling are derived, including dissipative and heat conduction, turbulence viscosity dissipation, heat release source term, then simplified the wave equation, transformed to cylindrical coordinate forms and solved, gas vibration frequency calculation formula are obtained.Second, combustion chamber finite element model established by Ansys/Mechanical software, six order of the combustion chamber natural frequency and the formation was obtained, change the diameter of the combustion chamber and wall thickness, length and boundary fixed mode, analyse the regulation of natural frequency change. Solving the acoustic resonance frequency cavity, get normal temperature and high temperature condition axial first-order acoustic resonance frequency were214.3Hz and433.7Hz.Third, establish the combustion chamber model, heat acoustic unsteady phenomena are numerical simulation by CFD method in the combustion chamber. Through the unsteady simulation of2d combustion chamber, the oscillation are analysis in the time domain and frequency domain, and the results showed that the fire oscillation frequency are not serious influenced by DC wind pressure, but for the flame oscillation strength influence is obvious; Along with the increase of the injection quantity, the combustion chamber inlet pressure oscillations strength linear increase, flame oscillation frequency also increased significantly; The combustion chamber of the increased the length of flame oscillation frequency linear increases; Comparison of the flame of pressure, speed, temperature oscillation relationships, by three oscillation frequency is consistent, the relationship between the phase is different.Fourth, to the combustion chamber3d model numerical simulation, get the three dimensional distribution of pressure and speed, temperature and particle jet parameters in combustion chamber, compared the influence of the dc wind speed and in the combustion, results show that:the wind speed of the dc increases compression of the flame width on both sides, but the effect on the stability of flame is not much, and the strength of swirling intensity have serious impact on the stability of the flame.